1. The Field of the Invention
This invention relates to an exhaust coupler for motor vehicles, and more particularly, to novel systems and methods for effectively absorbing bending and elastic displacement during running of a motor vehicle in order to minimize the effect of displacements to the engine on the exhaust system and for prolonging the useful life of vehicle parts.
2. The Background Art
There is a recent trend toward manufacture of vehicles with larger engines. Use of a larger engine in a vehicle increases engine roll vibration. Engine roll vibration is particularly severe when starting the engine, when shifting gears, and when the vehicle is suddenly stopped or started. These vibrations are directly delivered to the exhaust pipe which can be easily damaged if a proper coupling device is not used. Moreover, the exhaust pipe itself also exposed to distortion and stress caused by the road conditions.
Typically, a coupler (D) is installed to reduce and to absorb vibration, stress and heat expansion. As shown in FIG. 1, the decoupler D is usually installed between the engine (1) and the exhaust pipe (2), the exhaust pipe (2) being connected to a muffler (3) in order to emit the exhaust gas. However, the coupler and the exhaust pipe are often supported by a minimum number of lightweight hanger mounts. Therefore, the coupler installed between the engine and the exhaust pipe should have enough strength to support the coupler itself and the weight of the exhaust pipe, and also should have enough flexibility to absorb displacement between the engine and the exhaust pipe. In addition, the coupler also must be compact in order to be inserted between the engine and the exhaust pipe.
A number of attempts have been made in the prior art to design an effective coupler. One attempt to solve the problems of the prior art was demonstrated by an English patent, GB2,277,969A which forcefully determines a bending center to absorb bending stress. As shown in FIG. 6, an inner sleeve (6) is overlapped with an outer sleeve (5) with a space therebetween. The outer sleeve (5) has a wider diameter than the inner sleeve and the edge of the outer sleeve is bent inwardly. Meanwhile, the inner sleeve (6) has a circular notch (7) which has a smaller diameter than the wider diameter of the outer sleeve. A buffering member (8) is engaged in the pocket formed on both sides of the notch (7). A bellows (9) surrounds the cylindrical area of the inner sleeve (6). One side of the bellows (9) is attached to the surface between the bent area of the outer sleeve and the buffering member. The other side of the bellowS is attached to the surface of the inner sleeve. The bending center (C) is formed approximately at the center of the overlapping area. The buffering members and the bellows are designed to absorb axial displacement and bending displacement. Typically, axial displacement is caused by vibration of the engine or impact due to road conditions. Bending displacement is generally caused when the axis of the inner sleeve and the axis of the outer sleeve cross each other at an angle.
The prior art has some disadvantages which are generally recognized in the industry. The bellows (9) of the previous technology is exposed to the open air, so it can easily be damaged when a rock or other loose object hits it. And high temperature of the bellows, due to exposure to exhaust gases, accelerates oxidation of the bellows. Consequently, the prior art has low durability and a short lifetime.
Moreover, allowable bending displacement in prior art devices is very narrow because the displacement center (C) is positioned at the middle of the buffering member (8). The allowable displacement is limited by the height of the notch and the gap formed between the bent area of the outer sleeve and the inner sleeve below the bent area. When a sudden strong stress requiring large displacement is imposed, the inner sleeve (6) has to strike either the tip of the bent area or the outer sleeve. As a consequence, the area experiencing the collision become weak, causing shape deformation of the part or a hole in the structure. Moreover, the process of corrosion is accelerated because of the high temperature of the exhaust gas passing inside of the sleeves.
In addition, in the prior art, bellows (9) is easily damaged by impacts of the tip of bent area, resulting in a significantly shortened lifetime of the structure. Because the applicable range of motion of the prior art decoupler is limited, a different size decoupler was needed each different automobile model.
Those skilled in the art have also tried to increase the number of pleats in the bellows, consequently increasing the length of the decoupler, therefore requiring use of high quality materials in order to achieve a durable part. Such structures have not been economically feasible, however.